How do parasite and induced drag vary with airspeed?

How do parasite and induced drag vary with airspeed?

• A. Parasite drag increases with airspeed; induced drag decreases with airspeed; total drag typically has a minimum at some cruise speed.
• B. Parasite drag increases with airspeed; induced drag increases with airspeed; total drag has no minimum.
• C. Parasite drag decreases with airspeed; induced drag decreases with airspeed; total drag typically has a minimum at some cruise speed.
• D. Parasite drag decreases with airspeed; induced drag increases with airspeed; total drag increases.

Answer: (B)

Understanding how drag pieces behave with speed helps explain why the total drag curve has a minimum. There are two main drag components: parasite drag and induced drag. Parasite drag comes from air resistance on the airplane’s surfaces, fittings, and fairings, and it grows with speed—roughly proportional to V^2—because more air mass and flow interact with the surfaces as you go faster. Induced drag is tied to generating lift; to fly at a given weight, the wing must produce lift, and the vortices created by lift increase drag. As speed increases, the required lift coefficient drops, so induced drag falls roughly with 1/V^2. Put together, total drag D = parasite drag + induced drag rises at high speeds (because parasite drag dominates) and decreases at low speeds (because induced drag dominates as you approach a stall). The result is a U-shaped total drag curve with a minimum at some cruise or best-glide speed where the two effects balance. The statement that holds is: parasite drag increases with airspeed; induced drag decreases with airspeed; total drag typically has a minimum at some cruise speed.

Understanding how drag pieces behave with speed helps explain why the total drag curve has a minimum. There are two main drag components: parasite drag and induced drag. Parasite drag comes from air resistance on the airplane’s surfaces, fittings, and fairings, and it grows with speed—roughly proportional to V^2—because more air mass and flow interact with the surfaces as you go faster. Induced drag is tied to generating lift; to fly at a given weight, the wing must produce lift, and the vortices created by lift increase drag. As speed increases, the required lift coefficient drops, so induced drag falls roughly with 1/V^2. Put together, total drag D = parasite drag + induced drag rises at high speeds (because parasite drag dominates) and decreases at low speeds (because induced drag dominates as you approach a stall). The result is a U-shaped total drag curve with a minimum at some cruise or best-glide speed where the two effects balance. The statement that holds is: parasite drag increases with airspeed; induced drag decreases with airspeed; total drag typically has a minimum at some cruise speed.